A/C clutch not engaging

[haydenm315]

I am confused as to why my a/c clutch is not engaging. I've read that you are supposed to run the a/c system for 10 minutes once a month to keep it lubricated but it doesn't seem to want to work in cold weather. I think I found an explanation in the helms but it doesn't make sense if I'm supposed to be able to run the a/c system in the cold.
I read about something called an A/C cyclic switch. It's job is to control the electrical circuit to the a/c compressor clutch field coil. When the a/c cyclic switch contacts close, the signal to energize the a/c clutch is sent to the constant control relay module from the powertrain control module. The ccrm then supplies the voltage to energize the a/c clutch for a/c compressor operation. Here's the catch and where I'm confused. Ambient temperatures below 50 degrees fahrenheit during cold weather seasons prevents the a/c cyclic switch contacts from closing. This is due to the presure/temperature relationship of the refrigerant and the requirement of the system pressure to reach the pressure required to close the a/c cyclic switch contacts. How am I supposed to run my a/c compressor if it won't turn on when the temperature is below 50 degrees? Am I missing something here? Sdpatt to the rescue?

 

[SHO_Driver]

You can short the cycling switch with a jumper to run the a/c. But this could cause damage if the system has no freon inside.

 

[haydenm315]

SHO_Driver:
You can short the cycling switch with a jumper to run the a/c. But this could cause damage if the system has no freon inside.

I guess it's probably safer to check the pressure in the system before jumpering the system. The helms tells you to jumper before testing the pressure in the system. Go figure. I think there is a typo in my helms for the 1994 taurus. Section 12-00-28 for climate control system.
The first test on the page tells you to connect a gauge set to the charging valve cores and test for pressure above 50psi. Even if the pressure if above 50psi it says to do the same thing as if it wasn't and check for leaks and start the test over. The helms or maybe it was the haynes says to look around the fittings for greasy dusty residue which would indicate leaks. I had a new accumulator and compressor installed a year and a half ago. I knew enough that the clutch was bad on the compressor. I think I got ripped off and they gave me a new system with the exception of an evaporator which I just read is supposed to be changed at the same time. I just looked at my bill and I think I got ***** badly. How bad are these prices for a tempo?

$440 for the compressor
$91 for the accumulator
$40 for the diagnosis
$192 labor and charge
$20 waste disposal
$39 tax

$822 total on an initial $500 quote and it's broken less than 2 years later again. Talk about some bs. Is this legitimate or shoudl I go somewhere else? I really hate taking my car to shops and sho specialty shops are twice as bad in my opinion when it comes to pricing.

You're all gonna laugh at me, but I searched long and hard for something called an ambient temperature sensor. I finally came to the conclusion that this is just the temperature under the hood and there are no sensors to measure that. Am I correct with that assumption?

<small>[ February 23, 2003, 03:17 AM: Message edited by: haydenm315 ]</small>

 

[projectSHO89]

440 for the compressor was a bit high. Current list price for a Ford new one is $381.

Accumulator lists for $92.

The $20 waste disposal was bogus, as you still have the Tempo.

$192 labor wasn't a bad deal. The compressor is very difficult to access on a Tempo.

$39 dollars tax sounds like a ripoff, but not by the shop.

There is generally no reason to replace the evaporator core unless diagnostics indicate it is bad. That's the one that is inside the dash and is expensive laobor-wise to replace. The accumulator, also known as the receiver-dryer, is the part that is usually recommended for replacement along with the compressor.

BTW, are you working on the Tempo, or the SHO. Your post wasn't clear.

The first thing I would do is to check the static pressure in the system. The cycling switch requires 45 psi ascending in order to close. A low or weak charge will keep the switch open and prevent the clutch from engaging. When the ambient temp is too low, the static pressure inside the system will drop and the switch may remain open.

As far as I know, there isn't any under-hood ambient temp sensor that is used electrically by the AC to keep the clutch from cycling. If there is, I hope someone will point it out.

Steve

 

[rangerj]

Haydenm,

I do not know of an ambient temperature sensor switch "under the hood" of any make or model vehicle. That does not mean that such a thing does not exist, but if it does I have never seen one under the thousands of hoods I've have been under.

Next, the A/C clutch coil should be getting battery voltage, i.e. 12+ volts. You can measure this at the coil connection. The low pressure switch, which will not allow the compressor to be run if the pressure is less than, say 20 psi to 45 psi, depending on the system.

This switch is usually mounted on top of the filter/dryer, aka accumulator, on late model Fords. Late model to me is 1985 and newer.

You can jumper the connector to get the compressor to engage long enough to determine if the clutch coil is working, or not. There will be enough oil in the compressor to protect it for a short run.

The cause for concern is that if the refrigerant has leaked down, then some oil has also leaked out. This is because the oil and the refrigerant mix and circulate through the system together.

The signs of a refrigerant leak are black, oily, accumulation around any connection. Refrigerant oil attracts dirt and dust and readily mixes with it. You may also find such spots on your condenser (in front of the radiator).

As for the price you paid, it is high but it's an honest price. We cannot expect a garage owner or dealer to charge us the price for parts that we can get them for. The most common practice for pricing parts is for the shop owner to double what the parts cost him/her.

For example, if the part cost the shop $50, the shop will charge you $100. The profit on the parts is a ligitimate part of the garages business. The other part is the labor, that is the owners time. You want paid for your time at work don't you?

The diagnostic fee is also a charge for diagnostic time, and the use of diagnostic equipment. The labor charge, AND refrigerant charge, combined at $192 is very reasonable. How many hours did you get charged for at $75 to $80 an hour, which is a common going rate for labor.

The disposal fee is relatively new, say the last 10 to 15 years. The professional garages can no longer throw hasardous materials in the dumpster. They have to pay to have the stuff "properly" disposed of.

Many garages charge each customer a flat fee for this. The $20 you were charged sounds like this garage does this.

The tax you were charged is most likely a sales tax. It calculates out to 5%. You like your roads and bridges in good shape, don't you?

Ask our Canadian friends about the Provincial Sales Tax PLUS the Goods and Services Tax, totaling about 15% in Ontario Province. Other Provinces are similar. Ask a New Yorker (city) about sales tax!

Was it necessary to replace the filter dryer? Yes, because the compressor would not be covered under the warranty if you do not replace the filter/dryer. All of the wear and tear on the compressor end up in the filter/dryer. Remember this is a sealed system. Would you put a used oil filter on a newly overhauled motor?

You did not get ripped off. You paid the retail price for parts and labor. Could you have saved a lot of money doing it yourself? Yes. So, invest in the tools and the education, and then it is only a matter of your time! rangerj